1. Field of the Invention
The present invention relates to means for securing heat sinks in apparatus such as computers, and particularly to a clip assembly for attaching a heat sink to a computer electronic package.
2. Related Art
Developments in integrated circuits have resulted in greater circuit density and complexity, thus increasing heat generated by operation of such integrated circuits within an electronic package. Heat sinks are often attached onto the electronic packages to efficiently remove the heat.
Nowadays, a resilient clip is popularly used to attach a heat sink onto an electronic package such as a central processing unit (CPU). The clip engages with a socket of the CPU. However, the CPU bears an entire weight of the heat sink. If a large, heavy heat sink is employed, it is difficult for the assembly to pass a standard vibration test. Furthermore, when a large heat sink is attached to the CPU, it is difficult to ensure that the retaining forces applied by the clip are uniform. If the retaining forces are not uniform, the heat sink is unlikely to have uniform thermal contact with the corresponding surface of the CPU. In such case, the efficiency of heat dissipation is reduced.
Another means for attaching a heat sink on a CPU comprises four through holes defined in four corners of the heat sink, and four threaded holes defined in a mother board. Screws are extended through the through holes of the heat sink and engaged in the threaded holes of the mother board, thereby attaching the heat sink to the CPU. However, the heat sink is rigidly connected to the CPU. It is difficult to ensure that the heat sink applies uniform pressure on the CPU, thus tending to reduce the efficiency of heat dissipation. Furthermore, the rigid connection is prone to deform the mother board.
Therefore, an improved means for securing a heat sink which overcomes the above-mentioned problems is desired.
Accordingly, an object of the present invention is to provide a heat sink clip assembly for readily attaching a heat sink to an electronic package such as a CPU, and for readily detaching the heat sink therefrom.
Another object of the present invention is to provide a heat sink clip assembly which ensures that a heat sink applies substantially uniform pressure on an electronic package such as a CPU.
To achieve the above-mentioned objects, a heat sink clip assembly in accordance with a preferred embodiment of the present invention attaches a heat sink to a CPU that is mounted on a mother board. The clip assembly comprises a back plate, four posts, and four fasteners. Each fastener comprises a bottom engaging end, a narrowed neck, a top cap engagable on the neck, and a coil spring. The neck of each fastener is extended upwardly through a hole of the heat sink such that the engaging end abuts a base of the heat sink. The top cap is engaged on the neck, and the spring is disposed around the neck and seated on the heat sink. The fasteners are thus pre-assembled to the heat sink. Each post comprises a threaded end at a top thereof, and an annular groove defined in a middle portion thereof. The groove receives a plastic ring therein. The posts extend upwardly from the back plate, and are pressed upwardly through apertures of the mother board. The mother board is thus pre-assembled on the back plate. The engaging end of each fastener defines an internal threaded hole engaging with the threaded end of a corresponding post, thereby attaching the heat sink to the CPU. Engagement of each fastener with its corresponding post can be adjusted, so that the four springs cooperatively apply even clamping forces to the heat sink.
Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiment of the present invention with the attached drawings, in which: